In-trench tamping machine



ttes Patent 72 Inventor c6611 Judd R0. Box 94, Sonora, California 95370 [21] App]. No. 757,056 [22] Filed Sept. 3, 1968 [45] Patented Oct. 20, 1970 [54] lN-TRENCH TAMPING MACHINE 17 Claims, 12 Drawing Figs.

[52] U.S. Cl 94/49, 61/72.1 [51] Int. Cl 1201c 19/30 [50] Field ofSearch 6l/72.1; I 94/48, 49

[56] References Cited UNITED STATES PATENTS 2,659,281 11/1953 Lucas 94/49 3,058,404 10/ 1962 Widelo 94/49X 3,097,537 7/1963 Peterson 94/48X 3,162,102 12/1964 Juneau 94 49 3,259,035 7/1966 Pfundt... 94/49 3,308,729 3/1967 KCSIei 94 49 FOREIGN PATENTS.

888,976 9 1943 France. H

Primary Examiner-Jacob L. Nackenoff. v A tto r ney Flehr', Hohbach, Test, Albrittou and l-le rbcrt ABSTRACT: An earth tamping machine for use in a trench in which a pipe line or the like is being laid. A wheeled carriage supports an eccentric drive shaft, actuated by an internal combustion engine, which rapidly reciprocates tamping foot structures depending from the carriage at opposite sides thereof in straddling relationship to the pipe line. The eccentricity of the drive shaft may be adjustably varied by selectively positionable bushing structures interposed between the drive shaft and the tamping foot structures. Dust proof seals prevent clogging of the tamping foot structures during use.

Patented Oct. 20, 1970 Patented Oct. 20, 1970 3,534,669

Sheet 2 of 2 II III.

INVENTOR. (56/4 .0100

irranvI/i IN-TRENCH TAMPING MACHINE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to earth tamping devices and more particularly to a movable tamping machine which is capable of simultaneously tamping the earth on both sides ofa pipe line or the like as the same is being laid in an open trench. Laterally spaced tamping foot structures are supported on a movable carriage for rapid vertical reciprocation in response to actuation of a power source, such as an internal combustion engine mounted on the carriage, which actuates means for simultaneously reciprocating each of the tamping foot struc tures into tamping contact with the earth on each side of the pipe line.

The tamping foot structures include dust seal means to protect the same from becoming fouled when in use and such dust seal means are included in conjunction with guide tube structure depending from the carriage for operatively supporting a tamping rod and tamping pad secured thereto.

Eccentric drive shaft means is employed to simultaneously actuate the tamping foot structures. The tamping foot structures are mounted in operative connection with the shaft by bearing and bushing structures which permit selective adjustment of the eccentricity of the shaft to permit selective adjustment of the length of stroke of the tamping rod so that the compressive force applied by the tamping rod to the earth being compacted may be varied as may be required for a particular job.

2. Description of the Prior Art Wheeled movable tamping devices have been broadly known in the prior art heretofore, some of which have used an eccentric drive shaft to reciprocate a tamping foot structure. Illustrative patents in that regard are Cameron, U.S. Pat. No. l-,819,866, dated Aug. I8, 1931; and Wayer, US. Pat. No. 3,327,598, dated June 27, 1967.

However, so far as is known, no tamping machine has been devised or perfected heretofore which is capable of tamping simultaneously on both sides of a pipe line being laid in an open trench. Heretofore, it has been necessary to use nonwheeled manually held tamping devices and to duplicate use of the same along both sides of the pipe line being laid, thereby duplicating the time and amount of work performed because of the necessity to use a two man crew and two machines, or a single man crew who must reverse his field and pass alternately along both sides of the pipe line.

Also, so far as is known, the particular adjustable eccentric drive means of this invention, and the improved tamping foot structure disclosed herein, have not been known in the prior art or utilized heretofore.

With the present invention, effective tamping in a trench may be rapidly effected by a one man crew using the subject machine, thereby greatly simplifying tamping operations characteristic of prior known procedures and permitting completion of tamping operations in less time than heretofore possible and, accordingly, at a substantial savings in labor costs.

The patents above mentioned are characteristic of prior known tamping devices which are designed for use in flat surfaces, rather than in a trench for effecting simultaneous tamping on both sides ofa pipe line or the like being placed in the trench. The construction of the subject machine described herein insures effective and rapid tamping in the environment mentioned.

SUMMARY OF THE INVENTION The present invention relates to a machine for tamping earth. More particularly, this invention relates to an improved machine for simultaneously tamping the earth on both sides of a pipe line or the like being laid in an open trench. The subject machine is, in its preferred embodiment, fully portable and easily transportable to a job site and is movable thereat along the length of the pipe line being laid. In the embodiment illustrated, the machine is manually movable along the pipe line but, if preferred, self-propelled capability may be imparted to the machine also without departing from the spirit of this invention.

The present invention solves a problem encountered heretofore in the tamping field in that it has been necessary to utilize generally a handheld tamping device and to utilize the same along the side of the pipe line being laid in a trench and to repeat the operation along the other side of the pipe line. Such procedure heretofore has been effected by a crew of two men with two separate tamping devices or, alternatively, by a one man crew retracing his steps along the opposite side of the pipe line after one side has first been tamped, Such prior procedures are prompted by heretofore available tamping devices and are wasteful of time and man power, and accordingly, require unnecessary expenditures in labor costs by the contractor performing a particular job.

With the present invention, a more rapid tamping operation may be effected at a substantially reduced cost by employing the present tamping machine which incorporates therein im proved tamping means permitting simultaneous tamping along both sides ofa pipe line or the like being placed in a trench.

From the foregoing, it should be understood that objects of this invention include: the provision of a movable tamping machine capable of tamping both sides of a pipe line or the like being laid in an open trench; the provision of a wheeled tamping machine capable of in-trench use; the provision in a tamping device of an improved tamping foot structure and means for actuating the same to effect rapid tamping reciprocation of a pad carried on the lower end of such structure; the provision of dust seal means in conjunction with tamping foot structure of a tamping device to preclude fouling of the tamping foot structure; the provision of improved eccentric drive shaft means for actuating the tamping foot structure of a tamping device; and the provision in an eccentric drive shaft mechanism of a tamping device of adjustable bushing means to permit selective modification of the eccentricity of the drive shaft employed. These and other objects of this invention will become apparent from a study of the following detailed disclosure in which reference is directed to the attached drawings.

DESCRIPTION OF THE DRAWINGS FIG. I is a plan view of the subject tamping machine;

FIG. 2 is a side elevational view of the machine;

FIG. 3 is a vertical sectional view of the tamping foot structure and drive means of the machine taken in the plane of line 3-3 of FIG. 1;

FIG. 4 is a side elevation view of a portion of the drive means of the machine taken in the plane ofline 4-4 of FIG. 3;

FIG. 5 is a side elevation view of the drive shaft of the machine showing an eccentric section on one end thereof;

FIG. 6 is an end elevational view of the shaft section shown in FIG. 5;

FIG. 7 is a side elevational view of a bushing which is engageable over the eccentric end section of the drive shaft;

FIG. 8 is an end elevational view of the bushing shown in FIG. 7;

FIGS. 9 and 10 are end elevational views showing the bush ing of FIG. 7 engaged with the drive shaft eccentric end section of FIG. 5 in alternate positions of adjustable eccentricity;

FIG. 11 is an isometric view of a locking pin employed to maintain the bushing and shaft end section engaged after a preselected amount of eccentricity desired has been determined; and

FIG. 12 is a plan view, generally schematic in nature, showing the machine in position in a trench straddling a pipe line being laid to tamp on opposite sides thereof simultaneously.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 12, the subject machine, generally designated 1, is schematically shown in use in a trench 2 straddling a pipe line 3 (such as a water or sewer main) which has been placed in the trench and which will be covered with earth. Prior to such covering, tamping of the trench along both sides of the pipe line is required and is effected by the subject machine. With the illustrated embodiment shown herein, the subject machine is drawn manually along the length of the pipe line during the tamping operation. However, it should be understood that self-propelled capability may be imparted to the machine if desired.

Heretofore, as noted previously, in-trench tamping along a pipe line or the like necessitated use of a hand held tamper which required a double operation. With the subject, invention, a single pass for each level of earth placed along the length of the pipe line is all that is required to effect tamping thereof rapidly and effectively.

It should be understood, of course, that utilization of the subject tamping machine is not limited to the environment disclosed herein but that the same is usable in other environments which also require tamping along laterally spaced locations. Also, it should be understood that the subject machine may be produced in models of varying sizes to permit the same to accommodate pipe lines of various diameters.

General details of the machine are seen in FIG. 1 and 2. The preferred embodiment of the machine 1 illustrated comprises a carriage, generally designated 6, comprising a supporting platform defined by a flat, generally rectangular metal plate 7. Depending from opposite side edges 8 and 9 of the plate at the front edge thereof are generally triangular fenders 11 between which an axle 12 extends and is rotatably journaled in suitable bearings (not shown). Mounted on axle 12 at its opposite ends in known fashion are pneumatic wheel and tire assemblies 13. it should be noted that the wheels are laterally spaced a substantial distance from each other and that the area between the wheels beneath the carriage is unobstructed to permit the carriage to pass over and along the pipe line in straddling relationship as shown in FIG. 12.

A graspable handle 14, of steel of the like, is secured to the under surface of the carriage plate 7 in any suitable fashion, such as by welding. In the illustrated embodiment, the handle is generally U-shaped and is formed from a single length of hollow pipe bent to the desired configuration to facilitate grasping by the operator of the machine. As noted previously, the illustrated embodiment of the machine is made to be drawn manually but, if desired, mechanical drive means to positively rotate the wheels from the power source of the machine may be employed to impart self-propelled capability to the machine.

Mounted on carriage plate 7 is the power source mechanism which comprises part of the drive means for actuating the tamping mechanisms of the machine. in the preferred embodiment, such power source comprises a conventional internal combustion engine, designated 16, secured on the upper surface of plate 7 above wheels 13 in any known fashion, such as by bolting.

A pulley wheel 17 is mounted on a drive shaft 18 projecting from the engine and pulley wheel 17 is rotated in response to operation of the engine in known fashion. Passing over pulley wheel 17 is a Vee drive belt 19 which actuates other components of the drive means for the tamping mechanism to be described.

The drive means further includes a drive shaft 21 which extends transversely of the carriage plate adjacent the rear edge thereof. Drive shaft 21 is supported above the carriage by a pair of laterally spaced conventional pillow blocks 22 which in turn are secured to plate 7 by bolt and nut assemblies 23 extending through the plate. Thus, shaft 21 is mounted for rotation about a longitudinal axis thereof to effect actuation of tamping mechanism to be described. Such rotation is effected by a pulley wheel 24 mounted on shaft 21 and actuated by the aforementioned drive belt 19.

At its opposite ends 26 and 27, drive shaft 21 is operatively connected with respective tamping mechanisms of the machine, through an eccentric structure to be described.

Referring first to FIGS. 2 and 3, the tamping mechanism preferably employed will be described. Such mechanism comprises a pair of laterally spaced tamping foot structures, each of which is generally designated 28. The tamping mechanism further includes means for operatively guiding each tamping foot structure 28 which, in its preferred embodiment, comprises a guide tube structure including a guide tube 29 secured to the carriage plate 7 in any suitable fashion, such as by welding, which insures a dust proof connection between the upper end of the guide tube and the carriage plate as seen in FlG. 3. The guide tube is defined by an upper enlarged portion 31 and an integral reduced diameter lower portion 32. An elongated tamping rod 33 which defines part of the tamping foot structure extends through the reduced portion of the guide tube and projects from the lower end thereof. Cylindrical bearings 34 and 36 are positioned in the reduced portion of the guide tube and permit smooth reciprocating sliding movement of the tamping rod therein during the tamping operation. As required, a suitable lubricant may be introduced into the guide tube to facilitate reciprocal movement of the rod.

The lower end 37 of the tamping rod is threaded to receive thereon a tamping pad 38 defined by an enlarged shoe plate 39 of any suitable size. A circular shoe plate is suitable, and one having a diameter of four inches has been found effective, but other sizes and configurations may also be employed. Shoe plate 39 has welded thereto a threaded nut member 41 by means of which the shoe plate is secured to the lower end of the tamping rod. A jamb nut 42 is also threaded on the lower end of the rod in tight engagement with nut 41 of the tamping pad to preclude loosening of the pad during use.

The upper end 43 of the tamping rod projects into the enlarged portion 31 of the guide tube and is pivotally engaged therein with the lower end 44 of a connecting shaft 46 by means of a pivot pin nut and bolt connector 47, such components defining other parts of the tamping foot structure. The upper end 48 of the connecting shaft projects beyond the upper end of the guide tube and through plate 7 of the carriage to permit its operative connection with the drive shaft 21.

It is important that foreign matter, such as dust and dirt, be precluded from entering the guide tube 29 and for that purpose the machine is provided with effective dust seal structures at the respective lower and upper ends of the guide tube. The seal structure preferably provided at the lower end, generally designated 51, is defined by an expansible and retractable accordion sleeve, of rubber or like resilient material, which is capable of withstanding repeated elongation and contraction to which it is subjected during rapid reciprocating movement of the tamping rod 33. Suitable hose clamps 52, or equivalent devices, are employed to secure the upper and lower ends of the sleeve around the lower end of the guide tube 29 and the lower end 37 of the rod 33, as best seen in FIG. 3.

The dust seal structure preferably employed at the upper end of the guide tube, as seen in FIGS. 1 and 3, is defined by a resilient generally circular diaphragm 53, of rubber of like resilient material capable of repeated elongation and contraction, having an opening 55 through the center thereof to accommodate the upper end 48 of the connecting shaft 46 mentioned previously. Engagement of the diaphragm with the periphery of the connecting shaft is secure and snug to prevent dust entry along the length of the shaft. The diaphragm seal 53 is held in place by means of a generally circular hold down ring 54 secured by a series of bolts 56 threaded in bores provided in the upper surface of the carriage plate 7.

Provided in conjunction with the opposite ends of the drive shaft are means for mounting the respective tamping foot structures described for vertical reciprocal movement in their respective guide tubes to effect earth tamping. 1n the illustrated embodiment, such mounting means comprises an apertured bearing 58 provided at each end of the drive shaft. Each such bearing, as best seen in FIGS. 3 and 4, has a cylindrical extension 59 depending therefrom into which the upper end 48 of connecting shaft 46 projects. A bolt and nut connector 61 extends through the bearing extension 59 and the upper end of the connecting shaft to secure the bearing and the connecting shaft together. Upon vertical movement of the hearing, effected upon rotation of the drive shaft, rapid vertical reciprocation of the connecting shaft and the tamping rod and tamping pad connectedtherewith is effected. The speed of reciprocation of the bearing may be selectively varied in known fashion, such as by varying the speed of operation of the internal combustion engine 16. The number of cycles of reciprocation per minute of each of the tamping foot struc tures may be selected in accordance with the type of earth or other material being tamped, in accordance with known procedures.

To effect vertical reciprocation of each bearing 58 which actuates an associated tamping rod and tamping pad, each of the opposite ends 26 and 27 of the drive shaft 21 is provided with a reduced offset eccentric section 62, as illustrated in FIGS. 5 and 6. Such eccentric section is circular in cross section but the axis 60 of such section is offset from the axis 20 of the drive shaft as noted from FIGS. 5 and 6.

Under normal circumstances, engagement of the eccentric sections of the drive shaft with the respective bearings 58 would effect the vertical reciprocation of the tamping rod and tamping pad mentioned previously when the drive shaft is rotated. However, with such an arrangement, only one reciprocating stroke of a given size could be effected because of the fixed dimensional relationship of the eccentric end section of the drive shaft to the bushing interior.

An important feature of this invention resides in the provision of means to impart selective adjustability to the length of stroke imparted to the tamping rod by the drive shaft so that the force applied thereby may be selectively varied. Such selective adjustment is imparted by means ofa generally circular cylindrical bushing 63 having the configuration shown in FIGS. 7 and 8. Such bushing is longitudinally dimensioned to correspond substantially to the length of a reduced eccentric section 62 of the drive shaft. The bore 64 through the bushing, which is circular in configuration, has its axis 60 offset from the axis 65 of the bushing, as noted from FIGS. 7 and 8. The bushing bore corresponds generally to the outer dimension of the shaft eccentric end section 62 so as to be snugly yet slidably received thereon. When bushing 63 is positioned on the shaft end section, bushing axis 60 is coincident with axis 60 of the shaft end section.

Bushing 63, which is larger in external dimension than shaft 21 (Note FIG. 9) may be securely interconnected with the drive shaft end section for rotation therewith by slotted means provided in the exterior surface of the shaft and the interior surface of the bushing bore. Such slotted means comprises at least two peripherally spaced open slots 66 extending longitudinally of the eccentric shaft end section 62 from its outer end. Slots 66 open externally of the end section. At least one open slot 67 is provided internally of the bushing and extends longitudinally into the bushing from one end thereof. Slot 67 opens internally into the bushing bore. In the preferred embodiment shown, two bushing slots 67 are employed, although more bushing slots (or more shaft slots) may be provided to increase the adjustability of the drive means eccentricity.

Referring to FIGS. 9 and 10, when bushing 63 is positioned around the offset end section 62 of the drive shaft, the extent or degree of eccentricity imparted to the drive shaft may be varied in accordance with the position chosen for the bushing on the shaft. For example, as seen in FIG. 9, when both slots 67 of the bushing are aligned with both slots 66 of the eccentric shaft end, a stroke of predetermined extent determined by the dimensions of the bushing and shaft is imparted upon rotation of the shaft. With the embodiment illustrated, the minimum stroke position is seen in FIG. 9. However, as seen in FIG. 10 when only one of the bushing slots is aligned with one of the shaft slots, a different eccentricity results and a different stroke is produced. In the showing of FIG. 10, a longer stroke is imparted to the tamping rod than is produced with the FIG. 9 position.

According to the extent of stroke desired, the respective bushings 63 and eccentric shaft end sections 62 are aligned prior to use of the machine and such alignment is maintained by locking structure, in the form one or more cylindrical locking pins 68 received in each of the aligned slots, as seen in FIGS. 9 and I0.

The respective locking pins 68, bushings 63, and shaft end sections 62 are held in operative relationship during operation of the tamping machine by retainer structure. In the illustrated embodiment such retainer structure comprises a threaded bore 70 provided axially in the shaft end section 62 in which a bolt 72 is threadedly received. An enlarged washer 71 is interposed between the head of bolt 72 and the shaft end to prevent separation of the components described.

It should be understood, of course, that the degree of eccentricity may be selected within wide predetermined limits. determined by the number and spacing of the alignable slots 66 and 67 provided in the eccentric shaft end sections and in the bushings. The two position adjustability illustrated by FIGS. 9 and 10 is intended to be illustrative only.

It should also be understood that, upon actuation of the internal combustion engine, drive shaft 21 is rotated in accordance with the speed of the engine to effect reciprocation of bearings 58 mounted on the opposite ends of the drive shaft in which the eccentric shaft end-bushing structure just described is operatively positioned. Such bearing reciprocation effects vertical reciprocation, in turn, of the connecting shaft 46 and the tamping rod 33 connected therewith, at each end of the drive shaft. As a result, when the carriage is pushed, or pulled if preferred, along the length of the pipe line being tamped, the earth on either side of the pipe line is rapidly and firmly compacted by the respective tamping foot structures which are actuated by the drive shaft in the manner described.

Having thus made a full disclosure of a preferred embodiment of the improved tamping machine of this invention, reference is directed to the appended claims for a determination of the scope of protection to be afforded thereto.

IClaim:

l. A self-supporting in-trench earth tamping machine for tamping simultaneously along both sides of a pipe line or the like, comprising:

a. a movable carriage including laterally spaced wheel assemblies beneath said carriage, the area between said wheel assemblies being unobstructed so that said carriage may pass through a trench in straddling relationship relative to said pipe line therein;

. a pair of laterally spaced, reciprocal tamping foot structures depending from opposite sides of said carriage and positioned for straddling said pipe line;

c. means on said carriage mounting said foot structures for generally vertical reciprocating movement; and

d. adjustable drive means for simultaneously actuating said means mounting said foot structures to effect rapid reciprocating movement of said foot structures relative to the earth to be tamped thereby.

2. The tamping machine of claim 1 in which said drive means comprises:

a. a drive shaft extending transversely of said carriage having eccentric sections thereon adjacent opposite ends thereof operatively connected with said means mounting said foot structures for reciprocating movement; and

b. a power source mechanism for rotating said drive shaft.

3. The tamping machine of claim 2 in which said drive means further includes:

a. bushings adjustably positioned on said drive shaft in engagement with each of said shaft eccentric sections whereby the eccentricity of said shaft sections may be selectively varied; and

b. locking pin structures maintaining said bushings in preselected positions of adjustment relative to the associated shaft eccentric sections, and in which said mounting means for said foot structures comprisesbearing structure operatively interposed between and interconnecting said shaft eccentric sections and said bushings with said foot structures.

4. The tamping machine of claim 1 which further includes guide means including a guide tube in which each of said foot structures is rcciprocablc, and in which each of said foot structures comprises:

a. an enlarged tamping pad for engagement with the earth to be tamped; and

b. a rod positioned in its associated guide tube on the lower end of which said pad is mounted, and in which said means mounting each of said foot structures for movement comprises connecting mechanism operatively connecting said rod with said drive means whereby reciprocating movement of said rod in said tube is cffected when said drive means is actuated.

5. The tamping machine of claim 4 in which said connecting mechanism comprises:

a. a connecting shaft interposed between said rod and said drive means;

b. the lower end of said connecting shaft being pivotally connected with said rod; and

c. the upper end of said connecting shaft being generally rigidly connected with said drive means.

6. The tamping machine of claim 2 which further includes guide means including a guide tube in which each of said foot structures is reciprocable, and in which each of said foot structures comprises:

a. an enlarged tamping pad for engagement with the earth to be tamped; and

b. a rod positioned in its associated guide tube on the lower end of which said pad is mounted; and in which said means mounting each of said foot structures for movement comprises connecting mechanism operatively connecting said rod with said drive shaft whereby reciprocating movement of said rod in said tube is effected when said drive shaft is actuated.

7. The tamping machine of claim 6 in which said connecting mechanism comprises:

a. a connecting shaft interposed between said rod and said drive shaft;

b. the lower end of said connecting shaft being pivotally connected with said rod; and

c. the upper end of said connecting shaft being generally rigidly connected with said drive shaft.

8. An in-trench earth tamping machine for tamping simultaneously along both sides of a pipe line or the like, comprising:

a. a movable wheeled carriage;

b. laterally spaced, reciprocal tamping foot structures depending from opposite sides of said carriage and positioned for straddling such pipe line;

c. an eccentric drive shaft supported by and extending transversely. of said carriage having offset sections adjacent its ends;

d. adjustable bushing structures interposed between said shaft offset sections and said tamping foot structures operatively and selectively adjustably connecting said foot structures with said shaft sections; and

e. a drive engine on said carriage operatively connected with said drive shaft to rotate said shaft to effect rapid reciprocating movement of said foot structures relative to the earth to be tamped thereby.

9. The tamping machine of claim 8 in which said drive shaft includes at least two peripherally spaced open slots extending longitudinally thereinto from each of its ends and in which each of said bushing structures comprises:

a. a bushing positioned on said drive shaft in engagement with an offset eccentric section thereof;

b. at least one open slot extending longitudinally into such bushing from an end thereof;

c. each said bushing being positioned on its associated shaft section with a bushing slot selectively aligned with a shaft section slot in accordance with the amount of eccentricity desired; and

d. a locking pin received in said aligned slots maintaining each bushing in such preselected position of adjustment relative to its associated shaft offset section.

10. The tamping machine of claim 9 which further includes bearings interposed between said bushings and said tamping foot structures permitting rotation of said drive shaft to effect reciprocation of said foot structures.

11. The tamping machine of claim 10 which further includes means for guiding each of said tamping foot structures, comprising a guide tube secured to said carriage and depending therefrom, and in which each of said tamping foot structures comprises:

a. a rod reciprocally movable in its associated guide tube and projecting from the lower end of said tube;

b. a connecting shaft reciprocally movable in said tube and projecting from the upper end thereof pivotally connected with the upper end of said rod and operatively connecting said rod with said bearings whereby reciprocating movement of said rod in said tube is effected when said drive shaft is actuated; and

c. an enlarged tamping pad on the lower end of said rod outside said tube.

12. The tamping machine of claim 11 which further includes dust seal structures at the lower end and upper end of said tube precluding entry of foreign matter into said tube.

13. The tamping machine of claim 12 in which said dust seal structures comprise:

a. a resilient diaphragm snugly surrounding said connecting shaft and secured to said carriage at the upper end of said tube; and

b. an expansible and retractable sleeve secured to said tube and said rod adjacent their respective lower ends and secured respectively thereto.

14. in a tamping machine, improved tamping foot structure which is reciprocally actuatable by drive means supported upon a carriage, comprising:

a. an elongated guide tube secured to and depending from the under surface of said carriage in dust tight engagement therewith; and

b. an elongated tamping rod slidably positioned in and operatively engaged with a reduced size guide portion of said tube;

l. the lower end of said rod projecting from the lower end of said tube,

c. a connecting shaft pivotally connected with the upper end of said tamping rod within said tube;

1. the upper end of said connecting shaft projecting from the upper end of said tube through and above the upper surface of said carriage,

2. said upper end of said shaft being operatively con nectable with said drive means on said carriage,

d. and enlarged tamping pad on the lower end of said tamping rod outside said tube; and

e. dust seal structures at both the lower end and the upper end of said tube to preclude entry of foreign matter into said tube, comprising;

1. a resilient diaphragm snugly surrounding and engaging said connecting shaft and sealing said upper end of said tube at said upper surface of said carriage,

. a hold down ring clamping said diaphragm against said carriage upper surface in dust sealing engagement therewith,

3. an expansible and retractable sleeve surrounding and engaging said lower end of said tube and said lower end of said rod and interposed therebetween, and

4. clamping means securing the opposite ends of said sleeve in dust sealing engagement with said tube and said rod lower ends.

15. In a tamping machine comprising tamping foot structure which includes a tamping rod, improved means for effecting reciprocal movement of said tamping rod, said means comprising:

a. a drive shaft rotatable by a power source of said machine;

b. an offset eccentric section on said shaft adjacent an end thereof;

l. at least two open slots extending longitudinally of said shaft into said eccentric section thereof,

2. each of said shaft slots opening externally of said shaft eccentric section,

c. a hollow bushing surrounding said shaft eccentric section in snug selectively rotatable relationship therewith;

l. at least one open slot extending longitudinally of said bushing,

2. said bushing slot opening internally of said bushing d. said bushing being adjustably rotatably positionable on ing movement of said tamping rod as recited in claim a. a bearing structure connected with an end ofsaid tamping rod; and

b. said bushing being rotatably receivable within said bearing structure whereby reciprocal movement is imparted by said bearing to said bushing and said rod upon rotation of said drive shaft.

17. The tamping machine of claim 15 which further includes:

a. a second tamping foot structure connected with the opposite end of said drive shaft by a second slotted eccentric shaft section as defined in claim 16;

b. slotted bushing and locking pin structure as defined in claim 16 at said other end of said drive shaft; and

c. said tamping foot structures being laterally spaced from each other so that said machine may straddle a pipe line or the like during tamping use thereof. 

